.prvy {
    background-color: lightblue;
    width: 200px;
    padding: 25px;
    border: 25px solid navy;
    margin: 25px;
    float:left;
}
.druhy {
    background-color: lightgreen;
    width: 200px;
    padding: 50px;
    border: 10px solid red;
    margin: 25px;
    float:left;
}
.treti {
    background-color: lightgray;
    width: 400px;
    padding: 50px;
    border: 30px solid black;
    margin: 25px;
    float:left;
}